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PostPosted: Sun Nov 27, 2011 5:46 pm 
Retro Guru

Joined: Tue Mar 24, 2009 6:10 pm
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Location: Kent,25 miles from France
Don't fancy paying £150+ to buy a tool to face my BB's and can't be arsed to take it to my LBS to have it done for a tenner etc.

But I do fancy getting my apprentices to make me one. :D :D :D

So, what is the thread that traditionally a BB is .

I think it's 1.370"x24tpi. But what is the thread angle ?

55 or 60 degrees ?? Or something else.

I take it one side is a RH thread and the other a LH ?

Anything else I need in order to specify the job to them ?

Thanks


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PostPosted: Mon Nov 28, 2011 10:16 am 
retrobike rider / Gold Trader
retrobike rider / Gold Trader

Joined: Mon Oct 15, 2007 9:05 pm
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I think you are a little confused my friend. Do you want to face your BB shell or do you want to cut/tap the threads? Its two seperate tools. It sounds like you want to tap threads in the post, but you say face in the title.

Either way, cutting/facing tools need to be really hard steel and making them from scratch is very difficult. That's why they ain't cheep.


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PostPosted: Mon Nov 28, 2011 7:45 pm 
Retro Guru

Joined: Tue Mar 24, 2009 6:10 pm
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Location: Kent,25 miles from France
Not confused, I want to face the BB to accept a HT2 type BB

Threads are fine. Not touching those,and if I were, I'd just buy a tap.Well,two actually as one is RH and the other LH

Most,if not all BB facing tools take their referance from the threads.And attempt to face the outer edge of the BB perpedicular to the threads.

If you look at most tools they thread two pieces of steel/aliuminium into the BB and the facing tools goes through the middle.

I have a design,a workforce and the eqpt to make the tool, but just need some detail of the thread form of a BB


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PostPosted: Mon Nov 28, 2011 9:07 pm 
Dirt Disciple
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Joined: Tue Jan 12, 2010 6:18 am
Posts: 63
Location: Cheddar
Can you not just use a thread pitch gauge.


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PostPosted: Mon Nov 28, 2011 11:35 pm 
Retro Guru

Joined: Tue Mar 24, 2009 6:10 pm
Posts: 939
Location: Kent,25 miles from France
Don't walk wrote:
Can you not just use a thread pitch gauge.


Might have to.

Just thought someone may now the exact thread form. Not sure it actually matters.................May get teh apprentices to do some leg work,rather than me.Or i may have to dust off my thread book.Dam,why did I not think of that first :oops:


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PostPosted: Mon Nov 28, 2011 11:50 pm 
Old School Grand Master
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Location: No brakes? Way to commit soldier.
Unless the frame is a very old Raleigh, with a Whitworth thread, then its going to be 60 degrees isn't it?


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PostPosted: Tue Nov 29, 2011 1:24 pm 
Retro Guru
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Joined: Tue Aug 07, 2007 12:22 pm
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Location: Platsa, Messinias, Greece
AS far as I'm aware English BB threads are 1.375" x 24TPI, Whitworth form (ie 55°). ISO are 1.37" x 24TPI, 60°.

The two are, to all intents and purposes, interchangeable so you could just go with the ISO standard.


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PostPosted: Tue Nov 29, 2011 6:59 pm 
Retro Guru

Joined: Tue Mar 24, 2009 6:10 pm
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Location: Kent,25 miles from France
Thanks for all your help.
My book of "world threads" at work told be all.

It's a BSC thread form. (British Standard Cycling)

Essentially a very rounded 60 degree thread form.1.370" 24tpi.

So, now to get my labour enregised and on the case


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PostPosted: Tue Nov 29, 2011 8:34 pm 
Retro Guru
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Location: Platsa, Messinias, Greece
Yes, sorry - I don't know why I thought it was 60° and not 55°. As a toolmaker (in a former life) I should know these things......... :oops:

Get those apprentices whipped into shape - it can be a bit like herding cats though.


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PostPosted: Tue Nov 29, 2011 8:37 pm 
Section Moderator & South West AEC
Section Moderator & South West AEC
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Joined: Mon Jun 25, 2007 3:33 pm
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Location: new forest
if you can make them for sensible money would it be worth selling a few?

depending on price i'd be interested.


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